from ClickHouse Release 19.17.6.36, 2019-12-27

ClickHouse release v20.11.2.1, 2020-11-11

• If some profile was specified in distributed_ddl config section, then this profile could overwrite settings of default profile on server startup. It’s fixed, now settings of distributed DDL queries should not affect global server settings. #16635 (tavplubix).
• Restrict to use of non-comparable data types (like AggregateFunction) in keys (Sorting key, Primary key, Partition key, and so on). #16601 (alesapin).
• Remove ANALYZE and AST queries, and make the setting enable_debug_queries obsolete since now it is the part of full featured EXPLAIN query. #16536 (Ivan).
• Aggregate functions boundingRatio, rankCorr, retention, timeSeriesGroupSum, timeSeriesGroupRateSum, windowFunnel were erroneously made case-insensitive. Now their names are made case sensitive as designed. Only functions that are specified in SQL standard or made for compatibility with other DBMS or functions similar to those should be case-insensitive. #16407 (alexey-milovidov).
• Make rankCorr function return nan on insufficient data https://github.com/ClickHouse/ClickHouse/issues/16124. #16135 (hexiaoting).
• When upgrading from versions older than 20.5, if rolling update is performed and cluster contains both versions 20.5 or greater and less than 20.5, if ClickHouse nodes with old versions are restarted and old version has been started up in presence of newer versions, it may lead to Part ... intersects previous part errors. To prevent this error, first install newer clickhouse-server packages on all cluster nodes and then do restarts (so, when clickhouse-server is restarted, it will start up with the new version).

ClickHouse release v20.10.3.30, 2020-10-28

• Make multiple_joins_rewriter_version obsolete. Remove first version of joins rewriter. #15472 (Artem Zuikov).
• Change default value of format_regexp_escaping_rule setting (it’s related to Regexp format) to Raw (it means – read whole subpattern as a value) to make the behaviour more like to what users expect. #15426 (alexey-milovidov).
• Add support for nested multiline comments /* comment /* comment */ */ in SQL. This conforms to the SQL standard. #14655 (alexey-milovidov).
• Added MergeTree settings (max_replicated_merges_with_ttl_in_queue and max_number_of_merges_with_ttl_in_pool) to control the number of merges with TTL in the background pool and replicated queue. This change breaks compatibility with older versions only if you use delete TTL. Otherwise, replication will stay compatible. You can avoid incompatibility issues if you update all shard replicas at once or execute SYSTEM STOP TTL MERGES until you finish the update of all replicas. If you’ll get an incompatible entry in the replication queue, first of all, execute SYSTEM STOP TTL MERGES and after ALTER TABLE ... DETACH PARTITION ... the partition where incompatible TTL merge was assigned. Attach it back on a single replica. #14490 (alesapin).
• When upgrading from versions older than 20.5, if rolling update is performed and cluster contains both versions 20.5 or greater and less than 20.5, if ClickHouse nodes with old versions are restarted and old version has been started up in presence of newer versions, it may lead to Part ... intersects previous part errors. To prevent this error, first install newer clickhouse-server packages on all cluster nodes and then do restarts (so, when clickhouse-server is restarted, it will start up with the new version).

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